Apoptosis, or programmed cell death, is thought to play an important role in the loss of neurons due to ischemic stroke and other neurodegenerative conditions. Apoptosis has also been implicated in the death of cells occurring in certain immune disorders, polycystic kidney disease, and cardiac myopathy. The ICE proteases are key mediators of apoptosis and ICE protease inhibitors can block programmed cell death in vitro and in vivo. CoCensys has discovered, through screening chemical libraries, three chemically-distinct classes of small molecules (non-peptides) which inhibit the activity of two of these apoptotic proteases, CPP32 and ICE. We propose to complete the in vitro characterization of these inhibitors by determining whether they are selective for ICE proteases over other classes of proteases. We also propose to establish whether these ICE protease inhibitors are cytoprotective in tissue culture models of apoptosis. Finally, we will design and synthesize analogs of these compounds in order to increase their potency and cell permeability. These studies are important steps towards our longer-term goal of testing the activity of these compounds in animal models of apoptosis. PROPOSED COMMERCIAL APPLICATION: This research will potentially result in drugs which can be used to prevent the death of neurons due to ischemic stroke or other neurodegenerative disorders.